Why is this important to maintain? People have been complaining about this since the beginning, but I've never seen anyone actually articulate what the problem is.
Before React and this generation of frameworks, we had jQuery. In the jQuery world your site should work without JS. The page downloads, it's a usable page, and then your script starts attaching to elements to make the page more dynamic and responsive, if possible. If not, you still have the page.
It seems to me that progressive enhancement was a genuinely great idea, but somehow the true concept got lost. Nowadays some insist it's ok to have a site that won't begin to do anything without JS, but at the same time it's not OK to mix JS into the HTML code. That somehow we're preserving the purity of HTML as a display layer just by putting it in a separate file.
The biggest pet peeve of mine is when I'm presented a UI that doesn't function because the javascript hasn't loaded yet.
Do not show me a UI if it doesn't work when I press/touch it. More, if I visit your site and your UI doesn't present itself within 1-3s, there should be some alternative UI presented that explains why (rather than just a white page).
Why is this important to maintain? People have been complaining about this since the beginning, but I've never seen anyone actually articulate what the problem is.